From Digital and Analogue Instrumentation: Testing and Measurement

15.1 Introduction

Almost all measuring instruments provide the user with a quantitative measurement. The user always expects a known level of confidence in that measured value. The ultimate aim of a measurement is to have accuracy, reliability and confidence in the exercise of measurement and its quantitative output.

Calibration is the process that ensures accuracy in a measurement, and makes the measurement and its process traceable to standards discussed in chapter 1. With the growing adoption of quality standards such as ISO9000, many institutes are paying more attention to calibration of instruments, because all measurements have a direct bearing on product quality or service quality.

Since the end of World War II, technical advances have permited scientists to reduce uncertainty in measurements dramatically. In the 1940s, working measurements were made with an analogue iron-vane or D'Arsonval meter. With care, uncertainties were in the range of 0.5 per cent of full scale, or 5000 p.p.m. As shown in Figure 15.1, that 5000 p.p.m. in the 1940s became 100 p.p.m. by 1960, 10 p.p.m. by 1970 and 2 p.p.m. today [1].

Figure 15.1: The trend towards lower uncertainties in working measurements (source: Reference 1)

This chapter provides an introduction to calibration of common instruments and the calibrators.

15.2 Metrology and calibration

Simply stated, metrology is the science of measurement. Everything that has to do with measurement, be it designing, conducting, or analysing the results of a test, exists within the realm of metrology. These things cover the range from the abstract, comparing...

Products & Services
Calibration and Reference Standards
Calibration standards and reference sources include any source that can provide a reference for the calibration of an instrument or comparison of a material or component.
Calibration Software
Calibration software is used to generate documentation of calibration results, calibration certificates and reports. It also provides lookups of calibration procedures and database functions.
Calibration Instruments
Calibration instruments use electrical signals or physical quantities to calibrate sensors and meters. Devices that produce electrical signals can serve as precise meters for sensor calibration, or send output signals to other devices.
Laboratory and Calibration Gases
Laboratory and calibration gases are specialized for use as laboratory standards, as well as for detection, sample preparation, environmental monitoring and analysis applications.

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